feat: add demo mode for testing and review purposes

- Activates by tapping "None (disable)" 7 times.
- Displays a confirmation message when `Demo Mode` is enabled.
- Simulates a connection to a Meshtastic device and allows the app to function without requiring real hardware.

app/src/main/java/com/geeksville/mesh/model/BTScanModel.kt

@@ -24,6 +24,7 @@ import com.geeksville.mesh.util.anonymize
 import com.hoho.android.usbserial.driver.UsbSerialDriver
 import dagger.hilt.android.lifecycle.HiltViewModel
 import kotlinx.coroutines.Job
+import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.catch
 import kotlinx.coroutines.flow.combine
 import kotlinx.coroutines.flow.launchIn
@@ -45,24 +46,27 @@ class BTScanModel @Inject constructor(
     val devices = MutableLiveData<MutableMap<String, DeviceListEntry>>(mutableMapOf())
     val errorText = MutableLiveData<String?>(null)
 
-    val isMockInterfaceAddressValid: Boolean by lazy {
-        radioInterfaceService.isAddressValid(radioInterfaceService.mockInterfaceAddress)
+    private val showMockInterface = MutableStateFlow(radioInterfaceService.isMockInterface)
+
+    fun showMockInterface() {
+        showMockInterface.value = true
     }
 
     init {
         combine(
             bluetoothRepository.state,
             networkRepository.resolvedList,
-            usbRepository.serialDevicesWithDrivers
-        ) { ble, tcp, usb ->
+            usbRepository.serialDevicesWithDrivers,
+            showMockInterface,
+        ) { ble, tcp, usb, showMockInterface ->
             devices.value = mutableMapOf<String, DeviceListEntry>().apply {
                 fun addDevice(entry: DeviceListEntry) { this[entry.fullAddress] = entry }
 
                 // Include a placeholder for "None"
                 addDevice(DeviceListEntry(context.getString(R.string.none), "n", true))
 
-                if (isMockInterfaceAddressValid) {
-                    addDevice(DeviceListEntry("Included simulator", "m", true))
+                if (showMockInterface) {
+                    addDevice(DeviceListEntry("Demo Mode", "m", true))
                 }
 
                 // Include paired Bluetooth devices

app/src/main/java/com/geeksville/mesh/repository/radio/MockInterfaceSpec.kt

@@ -1,15 +1,11 @@
 package com.geeksville.mesh.repository.radio
 
-import android.app.Application
-import com.geeksville.mesh.android.BuildUtils
-import com.geeksville.mesh.android.GeeksvilleApplication
 import javax.inject.Inject
 
 /**
  * Mock interface backend implementation.
  */
 class MockInterfaceSpec @Inject constructor(
-    private val application: Application,
     private val factory: MockInterfaceFactory
 ): InterfaceSpec<MockInterface> {
     override fun createInterface(rest: String): MockInterface {
@@ -17,6 +13,5 @@ class MockInterfaceSpec @Inject constructor(
     }
 
     /** Return true if this address is still acceptable. For BLE that means, still bonded */
-    override fun addressValid(rest: String): Boolean =
-        BuildUtils.isEmulator || ((application as GeeksvilleApplication).isInTestLab)
-}
+    override fun addressValid(rest: String): Boolean = true
+}

app/src/main/java/com/geeksville/mesh/repository/radio/RadioInterfaceService.kt

@@ -7,6 +7,7 @@ import androidx.lifecycle.Lifecycle
 import androidx.lifecycle.coroutineScope
 import com.geeksville.mesh.CoroutineDispatchers
 import com.geeksville.mesh.android.BinaryLogFile
+import com.geeksville.mesh.android.BuildUtils
 import com.geeksville.mesh.android.GeeksvilleApplication
 import com.geeksville.mesh.android.Logging
 import com.geeksville.mesh.concurrent.handledLaunch
@@ -104,8 +105,8 @@ class RadioInterfaceService @Inject constructor(
         return interfaceFactory.toInterfaceAddress(interfaceId, rest)
     }
 
-    fun isAddressValid(address: String?): Boolean {
-        return interfaceFactory.addressValid(address)
+    val isMockInterface: Boolean by lazy {
+        BuildUtils.isEmulator || (context as GeeksvilleApplication).isInTestLab
     }
 
     /** Return the device we are configured to use, or null for none
@@ -121,7 +122,7 @@ class RadioInterfaceService @Inject constructor(
         var address = prefs.getString(DEVADDR_KEY, null)
 
         // If we are running on the emulator we default to the mock interface, so we can have some data to show to the user
-        if (address == null && isAddressValid(mockInterfaceAddress)) {
+        if (address == null && isMockInterface) {
             address = mockInterfaceAddress
         }
 

app/src/main/java/com/geeksville/mesh/ui/SettingsFragment.kt

@@ -290,6 +290,9 @@ class SettingsFragment : ScreenFragment("Settings"), Logging {
             .show()
     }
 
+    private var tapCount = 0
+    private var lastTapTime: Long = 0
+
     private fun addDeviceButton(device: BTScanModel.DeviceListEntry, enabled: Boolean) {
         val b = RadioButton(requireActivity())
         b.text = device.name
@@ -299,6 +302,19 @@ class SettingsFragment : ScreenFragment("Settings"), Logging {
         binding.deviceRadioGroup.addView(b)
 
         b.setOnClickListener {
+            if (device.fullAddress == "n") {
+                val currentTapTime = System.currentTimeMillis()
+                if (currentTapTime - lastTapTime > TAP_THRESHOLD) {
+                    tapCount = 0
+                }
+                lastTapTime = currentTapTime
+                tapCount++
+
+                if (tapCount >= TAP_TRIGGER) {
+                    model.showSnackbar("Demo Mode enabled")
+                    scanModel.showMockInterface()
+                }
+            }
             if (!device.bonded) // If user just clicked on us, try to bond
                 binding.scanStatusText.setText(R.string.starting_pairing)
             b.isChecked = scanModel.onSelected(device)
@@ -354,7 +370,7 @@ class SettingsFragment : ScreenFragment("Settings"), Logging {
         // If we are running on an emulator, always leave this message showing so we can test the worst case layout
         val curRadio = scanModel.selectedAddress
 
-        if (curRadio != null && !scanModel.isMockInterfaceAddressValid) {
+        if (curRadio != null && curRadio != "m") {
             binding.warningNotPaired.visibility = View.GONE
         } else if (bluetoothViewModel.enabled.value == true) {
             binding.warningNotPaired.visibility = View.VISIBLE
@@ -449,6 +465,9 @@ class SettingsFragment : ScreenFragment("Settings"), Logging {
 
     companion object {
         const val SCAN_PERIOD: Long = 10000 // Stops scanning after 10 seconds
+        private const val TAP_TRIGGER: Int = 7
+        private const val TAP_THRESHOLD: Long = 500 // max 500 ms between taps
+
     }
 
     private fun Editable.isIPAddress(): Boolean {